Pseudomonas aeruginosa can induce infections that lead to a rapid loss of visual function. The current therapy includes antibiotic treatment that reduces the bacterial burden, nevertheless tissue damage occurs as a result of an uncontrolled inflammation. Our preliminary experiments have uncovered that mice deficient for macro- phage migration inhibitory factor (MIF) were protected from acute P. aeruginosa keratitis. This improvement was manifested as improved bacterial clearance, decreased neutrophil infiltration, decreased inflammatory responses in the MIF-knockouts when compared to P. aeruginosa infected wild type control mice. These experiments led to the hypothesis that inhibition of MIF during P. aeruginosa keratitis will result in a controlled inflammation and will be therapeutically beneficial. We propose to pursue this hypothesis 1) by exploring the role of MIF in regulating the susceptibility to infection induced by a variety of cytotoxic and invasive clinical isolates of P. aeruginosa in a mouse model of keratitis. The innate immune response to P. aeruginosa-induced infection will be characterized in MIF knockout mice and compared to that in C57BL6 control mice. The inflammatory responses during infection, PMN recruitment and disease severity will be evaluated. In addition, we will assess 2) the prophylactic and therapeutic potential of small molecule inhibitors of MIF or anti-MIF antibodies in prevention and treatment of the P. aeruginosa corneal infections of C57BL6 mice. This will be achieved by determining the effect of MIF inhibition on disease development that will be characterized by analysis of the bacterial burden and PMN infiltration in the cornea after infection. Finally, we will evaluate 3) the role of MIF as a modulator of the inflammatory responses. In this aim we will identify MIF-dependent pro-inflammatory mediators whose expression is changed at RNA and/or protein level by either quantitative real-time PCR or ELISA. We will establish the molecular mechanism of MIF function by testing whether MIF regulates the expression of inflammatory mediators by affecting the MAPK signaling pathways or by overriding the glucocorticoid effects in the corneal epithelial cells during infection. The expected impact of the proposed project is to ascertain a new molecular target for therapy which, when inhibited, will control the inflammatory responses during infection, limit tissue damage and facilitate an efficient healing process. PUBLIC HEALTH RELEVANCE: Bacterial keratitis is a sight-threatening complication of contact lens wear and eye trauma and Pseudomonas aeruginosa is a commonly isolated pathogen that can damage the eye integrity during keratitis. We have identified an important molecule-macrophage migration inhibitory factor (MIF)-that is involved in the pathogenesis of P.aeruginosa-induced infection. The project investigates whether inhibition of MIF can be used as a therapeutic to reduce the level of inflammation and, thus, improve recovery from acute infection. Knowledge gained from these experiments will allow design of better drugs for eye infections that are not limited to P.aeruginosa induced keratitis, but also have broader applications.